JOHANNESBURG, South Africa (Reuters) -- The trial of six white South African policemen accused of setting dogs on three black immigrants is due to begin on Monday.

The alleged video-taped assualt shocked South Africa, while the trial follows recent cases involving white-on-black violence which had led to what some observers said were lenient sentences.

"There will be a lot of interest in this case and it will be examined closely," said Gareth Newham, an analyst at the Centre for the Study of Violence and Reconciliation.

The video showed three men, later identified as Mozambican illegal immigrants, apparently being taken from a police van and mauled about the face, limbs and, in one case, the groin by German shepherd dogs, as officers laughed.

The victims were repeatedly savaged by four police dogs and were beaten when they tried to fend them off. They were filmed by one of the policemen in what one man described in a comment to the camera as a training exercise.

The video-tape shocked South Africa when it was aired last year by the public broadcaster, which had obtained footage, and triggered a national debate about post-apartheid change.

The tape was allegedly made in 1998 and was reported to have been shown at police parties.

A Justice Ministry spokeswoman told Reuters the six would face charges including attempted murder, corruption and assault with intent to cause grievous bodily harm. They will be asked to enter a plea this week.

Three of the accused, who have all been on bail, have resigned from the police force. The others have been suspended pending the outcome of the trial.

Analysts say the incident has thrown the spotlight on racism and police brutality, legacies of white-minority rule which ended in 1994.

"It shows an old culture of the police in which they feel they can treat black people with impunity," said Newham.

Analysts say while the police force has made major strides in racial integration, it has a long way to go.